The thin client-server system, which uses a low-price and dedicated information processing apparatus having the minimum functions such as displaying on a screen, inputting by use of a key or a mouse, or the like, is well known in these days (refer to patent documents 1 and 2). Hereinafter, the information processing apparatus is called a thin client terminal. According to a thin client-server system described in the patent document 1 or the like, a thin client terminal is connected through a network with a server which unifies management of all resources of an application or the like. According to the thin client-server system, the server holds a program, data, a file of the application or the like, and the application is processed by use of a memory area which is reserved virtually in the server. A process executed by the thin client terminal is limited to a process of inputting and outputting data, and a process of displaying and handling an image on a screen. Consequently, it is possible that the thin client terminal works in an environment of a small memory and a small hard disc, since almost all processes are executed only by use of resource of the server.
As one of solutions for preventing loss and leakage of data due to loss or theft of PC (personal computer), the thin client is widely noticed. Since PC, which is used as the thin client terminal, is not equipped usually with HDD (hard disk drive) or a record drive, PC cannot hold information. Since any information is not leaked even when PC is stolen or lost, the thin client is most suitable for ensuring security. While there are several methods for the thin client system, the following method is effective from a security point of view. According to the method, the server transmits a screen image of application, which is executed by the server, in a pixel unit to the thin client terminal. Then, the thin client terminal receives information in the pixel unit and indicates the information just as it is (refer to patent document 3). Since only the screen image is transmitted, the method is called the screen image transferring method.
Moreover, it is also realizable to use a cellular phone as the thin client terminal. Consequently, it is possible to apply the thin client system to a new use that PCs in an enterprise and in a home are controlled remotely from a destination or the like (refer to patent document 2).
Patent document 1: Japanese Patent Application Laid-Open No. 2007-65835
Patent document 2: Japanese Patent Application Laid-Open No. 2004-348380
Patent document 3: Japanese Patent Application Laid-Open No. 2005-228227
Patent document 4: Japanese Patent Application Laid-Open No. 2007-156986